Fibers are commonly used as reinforcement elements to increase strength and durability of various elastomer materials and related products, for example, rubber tires or belts. Aramid fibers, such as Kevlar fibers, can exhibit poor adhesion to elastomers due to their high crystallinity and smooth outer surface. The surface of the fibers also can be chemically inert further reducing adhesion to other materials. The lack of adequate adhesion at the elastomer and reinforcement matrix interface often results in poor material performance and can limit potential applications of the elastomer materials.
Surface modification and treatment of fibers has been attempted to improve adhesion to elastomer materials. For instance, plasma treatment can increase rubber adhesion by increasing activation energy at the surface of the fibers or etching the fiber surface to increase its roughness. Other methods of promoting adhesion include using coatings or adhesives that are regularly applied to aramid cords to form outer surfaces that are more compatible with materials encapsulating the fibers. Adhesive systems can include multiple steps and require introduction of new materials to rubber products or fibers, both of which can increase time and cost associated with the manufacture of the products.
It is an objective of the present disclosure to alleviate or overcome one or more difficulties related to the prior art. It has been found that treatments of aramid fibers involving acid, microwave, mechanical bending, coupling agent contact and combinations thereof can beneficially modify the surface of aramid fibers and can increase the adhesion of the fiber surface to elastomer materials.